The permanent magnetic material is a fundamental functional material in electronic industry. As an important component of magnetic materials, the permanent magnetic material plays an important role in electronic industry, information industry, motorcycles, electronic tools and auto industry, etc. The permanent magnetic material is a functional material that generates the magnetic field. The permanent magnetic material for a traditional DC motor, no matter a sintered product or a plastic magnetic product, adopts a uniform material. After the dimension of the motor has been determined, the geometric dimension of the permanent material is determined. Therefore, the magnetic property of the permanent magnetic material can only be adjusted by changing the material (type of material and grade of the material), such as sintered NdFeB N 3 5 S H , N42SH; ferrite; bonded NdFeB BNM-10 (corresponding to MQ magnetic powder B), BNM-8SR (corresponding to MQ magnetic powder 14-12), AlNiCo or SmCo, etc. However, different types of permanent magnetic materials vary greatly in this property, including the maximum magnetic energy product (BH) max, residual magnetism Br, coercivity Hcj, magnetic induction coercivity Hcb, etc. For example, the most frequently used ferrite, bonded NdFeB and sintered NdFeB mainly represent this property, as shown in the table below:
TABLE 1main properties of Commercial MagnetsMagnetic propertyResidualMaximum magneticmagnetismCoercivityHcjenergy productMagnetsBr (T)(kA/m)(BH)max kJ/m3Ferrite0.3-0.44250-350 25-36Bonded NdFeB0.6-0.78500-130028-96Sintered NdFeB1.1-1.4 800-2400240-420
From Table 1 can we see that bonded NdFeB can basically be butt jointed with ferrite in a magnetic energy product. However, there is a big property blank between sintered NdFeB and bonded NdFeB. Therefore, these materials restrict magnetic circuit design and actual application greatly.
At present, the most frequently used is ferrite permanent magnet. Although the magnetic property is comparatively low, the low price decides the absolute share in conventional fields. With technological progress and rising requirements on light, thin, short and small automatic appliances and articles, demand of rare earth magnet with high magnetic energy product is raised increasingly. However, rare earth magnet with high magnetic energy product is expensive, which restricts development of many motors or permanent magnets. Therefore, a magnetic material with both low price and high magnetic energy product is needed.